How Has Atomic Theory Changed Over The Years

Development of the atom model from early days to present days

Scientists have come up with a range of different theory about the atomic structure through the past centuries. As new advanced technologies have invented through their research of atom, it is easier for scientist to create new theories throughout the future. This essay will explain the different changes of` atomic theory in order from the early days till now.

The atomic theory was first explained by Leucippus. He is a Greek philosopher who lived around the 400 B.C. During that era, people are trying to understand the way an object is made. Another Greek philosopher who said ‘it is possible to subdivide a material into smaller and smaller parts’, but according to Leucippus theory, therefore, ‘eventually you

will arrive at a point where the particles is so tiny it couldn’t be further be subdivided’. He called these particles Atomos which means indivisible/unbreakable. Furthermore his student, Democritus explained that atoms are all made from the same material but the atoms of different elements have different sizes and shapes. There was, they believed that there are four elements that all things are made from earth, water, air and fire

Around the year 1803s, an English, chemist school teacher, John Dalton, was able to purpose the very first atomic model. He viewed the atoms as tiny, solid balls, and came up with 4 theories.
(1) All toms of an element are identical in mass and properties, (2) Atoms are tiny, invisible particles, (3) compound are formed by a mixture two or more different kinds of elements, (4)atoms of different elements are different.

As the year passed by, 1856, Joseph John Thompson (J.J Thompson) is the person who discovered the electrons. He created the “Plum Pudding Model”. He suggest that electrons are randomly placed through atoms. The Atom contain negatively charged particles called electrons, and positive charged matters. He did his experiment based on using electricity by using a discharge tube (cathode ray tube). He exposed that an electric current can run from the cathode to the anode, by forming some kind of a ray. These ray lately become known as electrons.

Ernest Rutherford expanded on all the past research about atom.

He found out that the atom is mostly empty space, with electrons orbiting a fixed positively charged nucleus in set, predictable paths. His famous experiment was the gold foil experiment. His experiment was to emit alpha particles towards a thing piece of gold. When the radiation was shooting out, it was detected by the fluorescent and was able to make the alpha particles visible through a viewing of a microscope. For the results, most of the alpha particles went through the gold foil, which means that they mainly consist of empty space. A small number of alpha particles were deflected slightly which suggested that the nucleus was positively charged. Only a varied number of alpha particles were bounced back, which means that most of the mass is concentrated in the nucleus because it needed a strong repulsion in order to bounce back.

A physiology Niels Bohr, who happened to study about the atomic theories with Rutherford, did a modification with the model and proposed that the electrons orbit the nucleus at different energy levels. The electrons are able to move from one level to another by gaining or losing their energy

packets.

At the year 1927 Heisenberg introduced the uncertainty principle Werner Heisenberg was a physicist, born in Germany, 1901 and died in 1976. He introduced the Uncertainty Principle. It was also called as the Heisenberg’s Uncertainty Principle. This principle stated that the electrons moved in an indefinite velocity or momentum. It is impossible to determine simultaneously the position nor the velocity of the electrons or any other particles.

Atoms when joined together form the basic structure of everything surrounding us. Atoms contain protons, neutrons and electrons. As the result, the atomic model has been developing for the past few centuries. Many scientists have come up with different theories throughout their own experiment and expanding other scientist’s theories. This has therefore give us the atom that we have today

Bibliography
Great ideas of science: Atomic Structure by Rebecca L. Johnson
http://chemistry.tutorvista.com/organic-chemistry/werner-heisenberg-atomic-theory.html
https://www.tes.com/lessons/v-fjd5_4R5XZ-g/copy-of-atomic-structure
http://m.teachastronomy.com/astropedia/article/The-Structure-of-the-Atom